The energy for exciting the luminescent material is supplied in the form of microwave radiation. Such a lamp normally comprises a quartz bulb filled with a low-pressure inert gas. The quartz bulb is coated with metal halide salts. The microwave radiation is provided by a microwave generator or a magnetron and produces a plasma by ionizing the respective inert gas filling.
This plasma causes the metal halide salt to evaporate and the plasma and the metal halide salt in combination cause an emission of light. In addition, the light spectrum emitted can be influenced by doping the coating.
In hitherto known lamps of this kind, light was coupled out e.g. via an optical fiber or the like.
This was especially done for allowing, during production of the plasma by the microwave radiation, an adequate EMC (electromagnetic compatibility) when the lamp was being installed. This means that respective electric or electromagnetic effects that may be produced in the case of the above-mentioned lamp, in particular due to the microwave radiation, are to be prevented from negatively influencing other technical devices or living beings.
It is the object of the present invention to dispense with such optical fibers or the like and to provide a possibility of coupling light directly out of a respective lamp housing in a cost-efficient and easy manner.